Track followers for x-ray spot film devices



March 1, 1960 LE ROY 1. LEISHMAN 2,927,211

TRACK FOLLOWERS FOR X-RAY SPOT FILM DEVICES Filed July 7, 1958 2 Sheets-Sheet 1 INVENTOR.

March l, 1960 LE ROY J. LEISHMAN 2,927,211

TRACK FoLLowERs FOR x-RAY sPoT FILM DEVICES Filed July 7, 195s 2 Sheets-Sheet 2 INVENTOR.

United States Patient C TRACK FOLLOWERS FOR X-RAY SPDT FILM DEVICES Le R01,1 J. Leishman, Los Angeles, Calif. Application July 7, 1958, No. 746,756

1 Claim. (Cl. Z50-'66) Y The invention herein described relates to a track-following means and more particularly to trackfollowing means applicable to X-ray spot film devices. X-ray spot film devices are used by radiologists for making instantaneous radiographs of what is seen during a fluoroscopic examination. Such devices make it possible to make from one to four exposures on the same lilm. Apparatus of this kind is described in my Patent No. 2,817,766 and in Patent No. 2,811,648, issued to Simon Yerkovich and myself.

In the device of the latter patent, a carriage that holds and transports the film from a position outside of the X-ray beam must make successive excursions into and out of the X-ray beam and assume a. different position each time it comes into the X-ray eld so that a diderent portion of the iilm will be exposed during each successive excursion.

In the said device of said latter application, two homeposition tracks are provided to cooperate respectively with two pair of ball bearings that straddle stationary tracks when the carriage is in its home or rest position. Two pivoted tracks are movable independently into alignment with the said home tracks, but only one of the pivoted tracks at a time is aligned with its associated home track. The pivoted tracks are curved as shown in Fig. l hereof where they are indicated by the numerals 1 and 2, respectively. These tracks are so disposed that each one is capable of moving the carriage over a path that diverges away from an imaginary line 3 that is parallel to the home tracks 4 and 5, the direction of divergence of each track being opposite from that of the other. In physical embodiments of the device shown in the said application, the straight portion 6 of track l is parallel to both of the home tracks 4 and 5 when track 1 is aligned with track 4, but in current embodiments it is displaced laterally from what would be a linear extension of the home track 4 by substantially 21A". The straight portion 7 of track 2 is similarly displaced in an opposite direction with respect to its cooperating home track when it is aligned therewith.

If the ball bearing track followers are disposed on a line that is at right angles to the straight portions of the tracks as indicated in Fig. 2, the spacing between the ball bearings must be considerably greater than the width of the track even if the said ball bearings are to be in firm engagement with the sides of the intermediate sloping portions 8, Fig. 2. The reason for this will be obvious from an examination of Fig. 5 where the ball bearings 9 and are on a straight line 13 parallel to the side 11 of the carriage and therefore on a line that is at right angles to the home tracks, not shown. The ball bearings 9 and 3.9 are shown in engagement with opposite sides of the sloping or angled track 12. lf these xed ball bearings 9 and 10 were to traverse a portion of the track at right angles to their center line 13, it will be obvious from the drawing that there would be considerable space between the ball bearings and one or both sides of the track. The ball bearings 9 and 14 are shown on a line that is perpen- 2,927,211 Patented Mar. 1, 1960 ICC 2 dicular to the sides of the track, and it will be noticed how much closer these ball bearings are together. Because of the desirability of avoiding slop or play between Vthe ball bearing track-followers and the portions ofthe track being traversed, the spot lm device described in the aforementioned application was provided with a ball bearing on one side of the track that was spring-loaded toward the ball bearing on the other side of the track, as shown in Fig. 3, hereof. The ball bearings were thus kept in iirm engagement with the track regardless of its curvature or direction with respect to a line drawn between the centers of the ball bearings.

It is an object ofthe present invention to eliminate the sides of the straight portions of the track when the ball bearing followers are mounted at fixed inter-center distances, regardless of the angle between the said portions Vand the common center line of said followers.

Other objects will appear as the specification proceeds.

In the figures:

Fig. 1 shows the underside of a carriage with the attached ball bearing track followers shown in continuous lines in engagement with the home tracks of a spot ilrn device, and it shows other positions of the ball bearings and carriage in broken lines. This iigure is generally a section View taken through thetracks on a plane adjacent the track anges. f l

Fig. 2 illustrates, at the positions indicated by the arrows, the amount of play that would occur between ball bearings mounted on a line perpendicular to certain straight portions of the tracks if the spacing between the ball bearings were to be such that positive engagement would occur between the said xedbearings and other straight portions `of the track extending at an angle to the first mentioned portions.

Fig. 3 illustrates a former method ofmounting one of the ball bearings on a spring-loaded pivoted arm in order to keep both ball bearings in engagement with their associated tracks regardless of the angle of said tracks.

Fig. 4. This illustration shows the relationship of a pair of ixed ball bearings with respect to tracks A and A2 disposed at opposite angles and with respect to a third track A3 disposed at an angle that is midway between the angles of the other two tracks.

Fig. 5 is a diagram to show the amount of variation that must be provided between the centers of a pair of rotatable track followers if they are to engage a portion of a track that is at right angles to their center line as well as portions of the track that may be at other angles with respect to such center line.

The tracks that are normally employed in spot lm devices embodying the instant invention use tracks having an L-shaped cross section. The side or arm of the tracks l and 2 forming what-might be called the flange 15, is broken away in Fig. 1 throughout the greater portion of the length of the tracks in order to show the operation of the mechanism more clearly, and the ange is entirely cut away from the home tracks 4 and 5. This ligure might therefore be considered to be `a bottom View in longitudinal section of a portion of the spot lm device taken on a plane cutting through the tracks just above the track iianges. In spot film devices embodying the invention herein described, the anges of the home tracks 4 and 5 are used to mount the home tracks to the base of the apparatus.

The ball bearings 16 and 17 are shown mounted at a lixed distance on a center line 18 that is at an angle with of the sloping yorangularly disposed portions of the Qpivf oted track 1, and that their angle lWith'respect to these angularly disposed' portions is the same as theirY angle with respect to the home tracks,fb'u't in an opposite direcd tion. When the ball bearing trackfollowers have guided the carriage into the position in which the carriage is Vin- Y dicated bythe numeral 192, it will-beseen that the ball bearings l(here designated as 162 and 172) arevstill at the track Vthat their'common center line bore with respect to the sloping portion of the track, but the angle has been reversed againrbecause the track is now disposed. at the same angle as the home track 4.

Yn devices in which the invention herein described has been embodied, means are of Icourse' employed to keep the carriage 19 always oriented in the same direction.

These means include another carriageron'which carriageY 19is movably mounted somthat it may move in the direc- `same'angle :withrespect to the vstraight portion'of the v tions indicated by the arrow 22. 'The .second carriage on which carriage 19 is thus mounted isv constrained to move transversely Vonly in the directions indicated by the Y arrow 23. Such means of course do (not form` a part of the instant invention and are therefore'neithershwn nor described in thisapplication. 7

It .will be seen that the same reversals of angle take l place as the ball bearings 20 and 21 moveaway from the home track 5 and onto `the ysloping rstraight'portion of pivoted track 2, when track v2 is aligned with home track 5.

" 2,927,211 Y "f ,L ,Y s

v v Y h I .nr angle of the center line for the ball bearings, it is thus merely necessary to Idetermine the angle of ltlte'st'raight portions of deviation of adjacent the tracks and divide by 2. This will be clear from Fig. 4. The center line 24 of the rollers or ball bearings 25 yand26 in Fig. 4 is thus at an angle CBE with respectto track A and `at au angle DBE with respect -to trackA Thees angles are obviously the sameand are one-half of angle CBD. CBD isthesameasangleF." l Y" 'f The term angle of deviation used herein is the angle at 4which a straight portion ofV the trackdeviates from an adjacent -straightrportion ofthe track. The said angle of deviation is thus the difference -betweeny180 and Ythe angle formed by adjacent straight portions of the track that are mutually angulrlydisdposed.

- Track A3 Vis at right angles to the center line 24 of the rollers or ball bearings 25 and 26. YIt will be noted that at point E on ball bearing 25, there is considerableV space between the periphery ofY ball bearing ,and the adjacent edgeof track A3 and that there is a similar space on the opposite side of track A3 between it and the .nearest point on the periphery of roller or ball bearingZ. This is the condition that prevails as the vball vbearings 16 and y17 or 20 and 21 of Fig. l go around ,the curves of the tracks 1 and 2. In the operation of a spot film device, however, a little play in this position is of no moment, but it is important that the play be at a minimum between the ball kbearings and the home tracks and the various straight portions of the tracks 1 and 2. e

My claim is:

In an X-ray spot lm device having a cassette carriage that is to be moved selectively in various directions, a trackcomprising atleast one part and having a rplurality of substantially straight sections angularlyY disposed with respect to each other, and a pair of rollers mountedon said carriage and positioned to engage .opposite sides of said track, said rollers pivoted on centers having .la common center line whose angle with respect to any straight It the straightintermediate portion of track 1 is at an angle of'lS" with respect to the home track, the center line of the ball bearingsV 16 and`17 should be'disposed at an angle'of 9 with respect to a line that is perpendicular to the home track. This center line will thus be -at an angle ot 9 with respect to aline that is perpendicularto the straight sloping portion of track 1V, butthe'agle will be disposed in the opposite direction. In laying out the straight portion.

portion of said track is substantially half the angle of deviation between said straight portion andan adjacent References Cited in the ileof thisrpatent:

UNITED STATES PATENTS 2,552,858 Mueller et a1. May 155, 1951 2,811,648 Y Leishman et a1. oef.29, 1957 www 

